This type of housing must be mechanically strong in order to withstand laying and recovery operations which subject it to shocks, and also to withstand the high pressure that exists at the bottom of the sea. In addition, it must be well insulated electrically relative to the electronic circuits it contains, since these circuits may be at an electrical potential which is very different from that of the housing because of the way they are remotely powered from the ends of the cable. Finally, the housing must be effective at dumping the heat generated by the electronic circuits in order to prevent their operating temperature rising considerably which would impair their long term reliability. Present undersea cables operate at high data rates and are fitted with housings containing ever increasing densities of electronic circuits, and this increases the quantity of heat that needs to be dissipated. It is therefore necessary to increase the dissipation capacity of repeater housings, and to take care that such dissipation is uniform for all of the electronic circuits contained in a repeater.
French patent application No. 2 630 575 corresponding to U.S. Pat. No. 4,962,445 describes a housing comprising:
a thermally conductive rigid body in the form of a circular section cylinder closed in watertight manner at its ends;
thermally conductive rigid receptacles each having a face which is complementary in shape to the shape of the inside wall of the body, e.g. in the form of a 60.degree. sector of a cylinder, if there are six receptacles;
copper wire mats placed between the walls and respective faces of the receptacles to transmit heat from the receptacles to the body;
a mechanical device to press each receptacle and its mat against the wall, thereby ensuring good thermal contact between the mat and the receptacle and between the mat and the wall.
The mechanical device includes two split annular type springs placed at respective ends of the housing and each surrounded by the six receptacles. The receptacles bear against the annular springs via V-section supports. Each support bears against the outside wall of an annular spring via the inside walls of its V-shape. The outside walls of the V-shape constitute two bearing surfaces respectively for two receptacles. For a housing including six receptacles, there are three supports at each end of the housing.
Two receptacles are hinged to each support, with each receptacle including two pegs placed at respective ends of the receptacle in the vicinity of one of its long sides. The pegs of two receptacles hinged to the same support pivot in two very close together holes through the support. The two receptacles are free to rotate about these pegs when the set of receptacles is removed from the housing for maintenance operations. When the receptacles are placed inside the housing they no longer pivot, they bear constantly against the outside walls of the V-shape, and the assembly behaves as though the two receptacles and their two supports constituted a single rigid part subjected to radially-outward forces generated by the two annular springs.
Each support has a certain amount of freedom to move in translation in a radial direction in order to enable the springs to thrust the set of two receptacles and their mats against the wall. In addition, each support is free to rotate about an axis parallel to the axis of symmetry of the housing. By virtue of these two degrees of freedom, the forces exerted by the two springs are distributed over the ends of the six receptacles. The way these forces are distributed depends on the irregularities in the gaps that remain between the receptacles and the wall, and also on the irregularities of the distribution of matter within the copper wire mats. The size of the gap remaining between a receptacle and the wall depends in particular on the deformation to which the body is subjected by high, deep-sea pressure. It may also be affected by displacement of the receptacles due to a violent shock during laying. The forces exerted by a single spring on the ends of the six receptacles are interdependent. They are poorly determined and therefore poorly distributed because of this interdependence and because of the absence of any adjustment means. This gives rise to non-uniformity in the pressure on the various mats and consequently to non-uniformity in the thermal conduction between the receptacles and the wall. Some receptacles are therefore at a higher temperature than others for the same amount of heat generated by their electronic circuits.